Monday, October 6, 2008

Paleolithic Diet Clinical Trials Part II

There were a number of remarkable changes in both trials. I'll focus mostly on Dr. Lindeberg's trial because it was longer and better designed. The first thing I noticed is that caloric intake dropped dramatically in both trials, -36% in the first trial and a large but undetermined amount in Dr Lindeberg's. The Mediterranean diet group ended up eating 1,795 calories per day, while the paleolithic dieters ate 1,344. In both studies, participants were allowed to eat as much as they wanted, so those reductions were purely voluntary.

This again agrees with the theory that certain neolithic or industrial foods promote hyperphagia, or excessive eating. It's the same thing you see in low-carbohydrate diet trials, such as this one, which also reduce grain intake. The participants in Lindeberg's study were borderline obese. When you're overweight and your body resets its fat mass set-point due to an improved diet, fatty acids come pouring out of fat tissue and you don't need as many calories to feel satisfied. Your diet is supplemented by generous quantities of lard. Your brain decreases your calorie intake until you approach your new set-point.

That's what I believe happened here. The paleolithic group supplemented their diet with 3.9 kg of their own rump fat over the course of 12 weeks, coming out to 30,000 additional calories, or 357 calories a day. Not quite so spartan when you think about it like that.

The most remarkable thing about Lindeberg's trial was the fact that the 14 people in the paleolithic group, 2 of which had moderately elevated fasting blood glucose and 10 of which had diabetic fasting glucose, all ended up with normal fasting glucose after 12 weeks. That is truly amazing. The mediterranean diet worked also, but only in half as many participants.

If you look at their glucose tolerance by an oral glocose tolerance test (OGTT), the paleolithic diet group improved dramatically. Their rise in blood sugar after the OGTT (fasting BG subtracted out) was 76% less at 2 hours. If you look at the graph, they were basically back to fasting glucose levels at 2 hours, whereas before the trial they had only dropped slightly from the peak at that timepoint. The mediterranean diet group saw no significant improvement in fasting blood glucose or the OGTT. Lindeberg is pretty modest about this finding, but he essentially cured type II diabetes and glucose intolerance in 100% of the paleolithic group.

Fasting insulin, the insulin response to the OGTT and insulin sensitivity improved in the paleolithic diet whereas only insulin sensitivity improved significantly in the Mediterranean diet. Fasting insulin didn't decrease as much as I would have thought, only 16% in the paleolithic group.

Another interesting thing is that the paleolithic group lost more belly fat than the Mediterranean group, as judged by waist circumference. This is the most dangerous type of fat, which is associated with, and contributes to, insulin resistance and the metabolic syndrome. Guess what food belly fat was associated with when they analyzed the data? The strongest association was with grain consumption (probably mostly wheat), and the association remained even after adjusting for carbohydrate intake. In other words, the carbohydrate content of grains does not explain their association with belly fat because "paleo carbs" didn't associate with it. The effect of the paleolithic diet on glucose tolerance was also not related to carbohydrate intake.

So in summary, the "Mediterranean diet" may be healthier than a typical Swedish diet, while a diet loosely modeled after a paleolithic diet kicks both of their butts around the block. My opinion is that it's probably due to eliminating wheat, substantially reducing refined vegetable oils and dumping the processed junk in favor of real, whole foods.Here's a zinger from the end of the paper that sums it up nicely (emphasis mine):

The larger improvement of glucose tolerance in the Paleolithic group was independent of energy intake and macronutrient composition, which suggests that avoiding Western foods is more important than counting calories, fat, carbohydrate or protein. The study adds to the notion that healthy diets based on whole-grain cereals and low-fat dairy products are only the second best choice in the prevention and treatment of type 2 diabetes.

That study kicks ass. It's a shame it wasn't all over the media, but it's very encouraging.

It's interesting that the insulin and glucose changes happened within the first six weeks for the so-called Mediterranean diet group and then leveled off, but that the numbers kept decreasing for the Paleo diet group even after six weeks. The "Mediterranean" diet seems like a short-term band-aid, whereas the Paleo diet seems like the way to repair the body's glucose tolerance and insulin sensitivity for long-term health.

Something else I just noticed: the Paleo dieters ate a lot more fish, even though it was included in both diets.

Was calore intakes self-reported or did they measure it exactly? People are notoriously inaccurate in their calorie counts, so I don't put much faith in the calorie counts if they didn't actually confirm them. Maybe people ignored the lean meat advice and still lost weight.

Stephan, great review. Was there a change in caloric consumption reported in the 2nd study? Scanning it quickly, I didn't see it. I've never been one to believe the calories in/out was as simple as stated, but looking at these data has me thinking. The consensus diet consumed 350 calories per day more. Over the course of the study, that is 3.6 pounds. The difference in weight loss at week 12 is 3.5 pounds. Interesting, no?

So does this raise a flag for all those claiming metabolic advantage? Should the argument come from a health perspective? I just don't know. Sometimes I feel like the more I read and think I understand, the dumber I get.

I'm still not understanding how the paleo group ended up eating only about 1400 calories a day. If calories are the issue, then we're back to square one contesting the calorie is a calorie theory, which we know to be wrong.

And don't pre-agricultural peoples eat up to 3000-3500 calories a day? This is also the estimate for paleolithic diets, judging by Cordain's own research.

Good points. It would be interesting to see what these people would have looked like after a year.

Bruce,

Each patient did a 4-day weighed food record using a digital scale.

Brian,

I didn't see any baseline data in Lindeberg's paper so I don't know what the change was. The difference in weight loss wasn't just fat. The difference in fat mass loss was only 1.6 kg, while the rest was "fat-free mass" and water. So it actually doesn't agree with "calories in, calories out".

Gunther,

Keep in mind that both groups started off borderline obese. That level of caloric intake would not have been sustainable for them once they had burned off their excess fat. It would be interesting to see what caloric intake they would stabilize at upon reaching equilibrium.

Maybe they were following the rules on those days, but on their own the rules went out the window. Unless a study was done under metabolic ward conditions, the calorie intakes are always dubious IMO. You have to put subjects under lock and key with 24 hour observation, or calorie counts are just a wild guess.

Why do we use "calories" as a measuring tool anyway. Seems like it isn't accurate at all on what the body utilizes when we eat. We don't "burn" calories in our bodies anyway. We utilize everything differently. The only thing that "burns" calories are the scientists in the labs trying to determine what foods are "fattening" or not.

This is too bizarre. I also spent my childhood summers by the sea (near Nice) getting advice not to cut the fat off my meat. And I too am a PhD candidate in neuroscience (systems, electrophysiology of auditory cortex). But I do also remember our meals being extremely slow, with tons of salad and vegetables and tomatoes and courgettes and many other delicious locally grown veggies. Ah, yes, and the chocolate, and even a little wine. So how does the paleolithic diet square with getting your vit. K2 from wonders like pate and cheese? -marguet- @rutgers(edu)

I'm OK with good quality dairy. It's not paleo, but it is a good source of fat-soluble vitamins. I'm not strict about paleo. There are cultures who have successfully incorporated certain grains and dairy into their diets without ill effect. Several of the healthy cultures that Weston Price studied ate dairy, and a number of them ate grains (only one ate gluten though- sourdough rye). The grains were often thoroughly fermented, and always soaked or sprouted.

I try to focus on fermented dairy and concentrated sources of dairy fat like cream and butter.

About Me

I'm a writer and science consultant with a background in neuroscience and obesity research. I have a BS in biochemistry and a PhD in neurobiology. I'm the author of "The Hungry Brain: Outsmarting the Instincts That Make Us Overeat".

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